Deadlock fix candidate

[Pyun YongHyeon]

On Tue, Mar 01, 2005 at 09:29:34PM -0800, Doug White wrote:
 > Hey folks,
 > 
 > After consultation with alc and rwatson and (limited) testing by kris,
 > I've come up the following patch as a fix for the sparc64 deadlocks that
 > afflict the package cluster sparc boxes.  Its an exact copy of what alc
 > suggested (thanks :) ) and by assembly inspection generates the desired
 > code.  Originally I was going to redo the loop to be more like ipi_wait()
 > with the declared volatile pointer, but a cast does the job. :)
 > 
 > I'm trying to determine if this also fixes similar deadlocks/hangs on i386
 > and amd64. I haven't seen any assembly level changes with the patch on
 > amd64, but I'm trying again on a fresh source tree in case I have
 > pollution from test patches that cvsup hasn't caught. I can only reproduce
 > the hang on amd64, but adding any sort of debugging makes it go away.
 > 
 > Comments appreciated. If things look good I'll look to commit this
 > tomorrow evening unless events dictate otherwise. Thanks!
 > 
Confirmed on Ultra2. I always saw the lockups as soon as 
I started to download files from Ultra2 ftp server to fast
i386 box(P4, 3GHz). But I never saw the lockup in UltraAXe
(UP machine). With your patch it works like a charm. Now I can
continue to check other issues on hme(4) now. :-)

Thanks a lot. 
-- 
Regards,
Pyun YongHyeon
http://www.kr.freebsd.org/~yongari	|	yongari at freebsd.org